Wireless communications systems are used in a variety of telecommunications systems, television, radio and other media systems, data communication networks, and other systems to convey information between remote points using wireless transmitters and wireless receivers. A transmitter is an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal such as radio, television, or other telecommunications. Transmitters often include signal amplifiers which receive a radio-frequency or other signal, amplify the signal by a predetermined gain, and communicate the amplified signal. A receiver is an electronic device which receives and processes a wireless electromagnetic signal. A transmitter and receiver may be combined into a single device called a transceiver.
Transmitters, receivers, and transceivers often include components known as oscillators. An oscillator may serve many functions in a transmitter, receiver, and/or transceiver, including generating a local oscillator signal (usually in a radio-frequency range) for upconverting baseband signals onto a radio-frequency (RF) carrier and performing modulation for transmission of signals, and/or for downconverting RF signals to baseband signals and performing demodulation of received signals. Such oscillators may include components known as phase-locked loops (PLLs). A PLL may be a control system configured to generate an output signal whose phase is related to the phase of the input “reference” signal. A phase-locked loop circuit may compare the phase of the input signal with a phase signal derived from its output oscillator signal and adjusts the frequency of its oscillator to keep the phases matched.
Wireless communication devices are increasingly moving to the Long Term Evolution (LTE) standard or other standards based on orthogonal frequency-division multiplexing (OFDM) or single-carrier frequency-division multiple access (SC-FDMA) modulation. In order to achieve the high peak data rate and low latency mandated by multi-media applications of this system the bandwidth of the channel is generally far larger than legacy wireless systems. In order to allow efficient use of spectrum these systems frequently allocate small fractions of the total bandwidth to a user. The bandwidth and frequency range of this allocation can vary from subframe to subframe. The large bandwidth channels required for efficient use of mobile broadband protocols like LTE must be carved from increasingly crowded spectrum. As a result, numerous undesirable effects may occur, especially when a narrow band with allocation containing a single resource block at the edge of the channel is transmitted. For example, such undesirable effects may include, without limitation, receiver desensitivity due to transmitter baseband noise, spurious emissions and desensitivity due to intermodulation and other non-linear effects, and/or other problems.